1. Field of the Invention
The present invention relates to a cold storage tank unit and a refrigeration cycle apparatus using the same.
2. Description of the Related Art
In an air conditioner for a vehicle, for example, disclosed in JP-A 2004-51077 (corresponding to U.S. Pat. No. 6,701,731), a refrigeration capacity (cooling capacity) in an evaporator can be obtained even after a refrigeration cycle is stopped. That is, this air conditioner is provided with a cold storage heat exchanger, which has a cold storage material and is arranged in series with an evaporator of a refrigeration cycle, and a tank unit in which this cold storage heat exchanger and pump means for circulating liquid refrigerant are integrally built. Moreover, a liquid refrigerant tank part for storing liquid refrigerant is integrally formed under the tank unit. In this regard, as the above-mentioned cold storage heat exchanger is used a heat exchanger in which multiple refrigerant tubes are arranged in such a way as to pass through a container (e.g., shell) filled with a cold storage material, or a heat exchanger in which multiple cold storage containers each shaped like a cylinder, a ball, or a capsule and filled with a cold storage material are bundled and in which interspaces between the respective cold storage containers are used as passages for refrigerant.
When an engine of a vehicle is operated, a compressor of the refrigeration cycle is operated and the cold storage material in the cold storage heat exchanger is cooled by low-pressure refrigerant having pressure-reduced by an expansion valve, whereby cold is stored. In contrast, when the engine of the vehicle is stopped and the compressor is stopped, liquid refrigerant stored in the liquid refrigerant tank part is introduced into the evaporator by the pump means for circulating liquid refrigerant, and is evaporated by the evaporator. Furthermore, the evaporated vapor-phase refrigerant is introduced into the cold storage heat exchanger and is cooled and condensed by the cold (cold release) of the cold storage material and is stored in the liquid refrigerant tank part. This cycle is repeated to continue air conditioning while the engine of the vehicle is stopped.
However, the above-mentioned cold storage heat exchanger has a structure in which the shell or the cold storage container filled with the cold storage material is exposed to refrigerant and receives the pressure of the refrigerant. Hence, the shell or the cold storage container needs to be designed to endure the pressure of the refrigerant to thereby increase its thickness so as to secure strength. Hence, this hinders size reduction and causes to increase material cost because high-strength material needs to be selected.
In a vehicle air conditioner with a refrigerant cycle described in JP-A-2002-274165 (corresponding to U.S. Pat. No. 6,854,286, U.S. Pat. No. 6,691,527, U.S. Pat. No. 6,568,205) there are provided with a first evaporator for normally cooling air to be blown into a vehicle compartment, and a second evaporator provided with a cold storage material. In this case, when a vehicle engine is operated, the first evaporator cools air to be blown into the vehicle compartment, and the cold storage material is frozen in the second evaporator. Furthermore, in a maximum cooling mode (cold down mode), the air to be blown into the vehicle compartment is cooled by using both the first and second evaporators. In contrast, when a compressor of the refrigerant cycle is stopped by a stoppage of the vehicle engine, air to be blown into the vehicle compartment is cooled by a cold release of the cold storage material in the second evaporator.
However, because both the first and second evaporators are arranged in an air guiding case disposed in the vehicle compartment, the air guiding case becomes larger due to both the first and second evaporators. When the sizes of the first and second evaporators are made small, the cooling capacities of the first and second evaporators are deteriorated.